The present invention relates to a method for the production of quinone methides, and more particularly, it relates to a method for electrolytically oxidizing bis(4-hydroxyphenyl)methanes to produce hydroxyphenyl quinone methides.
Quinone methides are known to be useful as antioxidants as taught by Coppinger U.S. Pat. No. 2,940,988. Coppinger discloses the oxidation of dihyroxydiphenyl methane with lead dioxide or lead tetraacetate to produce a free radical which is subsequently reduced to quinone methide. Reference is also made to Bacha U.S. Pat. No. 4,032,547 which discloses an oxidation process for preparing quinone alkides from the corresponding tri-alkyl or phenyl hindered phenols. The oxidizing agent of Bacha is ferricyanide as the secondary oxidant in combination with persulfate as the primary oxidant.
Quinone methides are also useful starting materials in the preparation of dihydroxybenzophenones, as disclosed in our copending application Ser. No. P16502 (Docket C-33,135). The dihydroxybenzophenones may, in turn, be used as light stabilizing agents and precursors for epoxy resins, polycarbonate resins, and other thermoplastics.
While prior art methods of preparing quinone methides exist, to date those methods have not found significant commercial utility because of their cost, inefficiencies, or other drawbacks.
Accordingly, the need exists for a process by which large quantities of quinone methides can be produced economically and at high yields.